Fouling Monitoring and Mitigation of Monovalent Selective Anion Exchange Membranes to Be Used in Reverse Electrodialysis
| Autor: | Kotoka, Francis |
|---|---|
| Přispěvatelé: | Velizarov, Svetlozar, Garcia, Ivan |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: | |
| Zdroj: | Repositório Científico de Acesso Aberto de Portugal Repositório Científico de Acesso Aberto de Portugal (RCAAP) instacron:RCAAP |
| Popis: | Erasmus Mundus Master in Membrane Engineering for a Sustainable World (EM3E-4SW) Organic fouling phenomena predominantly restricts the behavior of Anion Exchange membranes (AEMs), thus reducing the obtainable net power density in reverse electrodialysis (RED). Consequently, we propose a monolayer surface modification of heterogeneous Ralex-AEMs with biocompatible poly(acrylic) acid (PAA) to enhance organic antifouling and monovalent membrane permselectivity. The AEMs were immersed in PAA aqueous solution for 24 h for surface modification. The modified membranes were physicochemical characterized via water contact angle (WCA), water uptake, ion exchange capacity, fixed charge density and swelling degree measurements. Their electrochemical characteristics were evaluated through cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The impact of recurring fouling and cleaning was assessed. Membrane fouling behavior and sulfate rejection were studied in the presence of humic acid (HA), using model NaCl aqueous solutions in a diffusion cell. The modified AEMs (PAA-AEMs) showed a sulfate rejection improvement by 36%-54%, and their hydrophilicity was enhanced by > 15 % with respective to their WCA values. The 3 g/L PAA based AEM achieved an antifouling resistance of 65.8% towards HA in comparison with the unmodified membrane. Recurring fouling and cleaning of the membranes was investigated using 25 ppm HA as the model foulant, and 0.1 M NaOH(aq) as the cleaning agent. In this case, the NaOH cleaning solution restored the membrane resistances almost to their original values after the first fouling and cleaning cycle. However, it failed in the second and third cycles due to the predominance of irreversible fouling and adsorption caused by the HA, leading to higher membrane resistance. Overall, the results demonstrate the technical feasibility of the proposed membrane surface modification procedure, and the need for efficient cleaning agents to mitigate fouling of AEMs. This study may therefore provide a viable approach to enhance RED process efficiency. |
| Databáze: | OpenAIRE |
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